Audio amplifiers are used in a variety of applications ranging from consumer audio systems to high-end professional applications including audio mixing and/or audio compressing. For many of these applications, the audio processing system amplifies an electrical audio signal received from an input source to move a speaker cone back and forth. In general, an audio processing system monitors an amplified electrical output signal to ensure proper operation of an amplifier and prevent clipping of the amplified electrical output signal. For example, the portion of the amplified electrical output signal larger in magnitude than the voltage supply of the audio processing system is clipped or eliminated. The clipping results in distortion of the amplified electrical output signal. Ideally, the audio processing system prevents the generation of distorted audio music that can destroy audio speakers and/or audio amplifiers as a result of the clipping.
Multi-channel audio processing systems are frequently used in residential homes, corporations, and schools in which audio music needs to be sent to one or more rooms. These audio processing systems may manipulate audio music derived from an input source (e.g., CD players, DSS receivers, DVD players, tuners, or tape decks). The various input sources generally require different amplification levels for numerous reasons. First, the input sources as compared to each other have different average and peak voltage levels due to gain mismatches in decoding, demodulating, and converter circuitry associated with the input sources. Second, the input sources as compared to each other have different average volume levels of recorded materials due to variations from artist to artist. Third, the sources as compared to each other have different average volume levels of recorded materials due to variations in the recording and mixing processes in the recording studio.
For example, the peak output voltage and dynamic range of digitally recorded content on CDs is very large as compared to that of a compressed AM or FM radio signal. These variations result in significant volume differences input into an amplifier from one source to the next. If the gain of an amplifier is set to amplify a low volume output signal with a minimal dynamic range, then the amplifier can clip a later source with a high volume output signal with a large dynamic range. The clipping results in audible distortion of the source and potential damage to the amplifier, speakers or both.
Previous attempts for preventing clipping have involved controlling the audio output signal of the audio processing system in relation to the audio input signal. One previous attempt presets the amplifier gain to a low level to prevent clipping regardless of the input source. However, the consumer experiences differences in audible levels between low volume input sources and high volume input sources. Low volume input sources may not receive sufficient amplification due to the small preset amplifier gain. A second previous attempt uses fast reacting gain limiting technology to prevent an output audio signal from clipping by quickly adjusting the amplifier gain. However, the fast reacting gain limiting technology creates distortion of the output audio signal and a reduction or compression of the dynamic range. A third previous attempt adjusts the volume manually to prevent clipping of the output audio signal. However, eliminating clipping may be difficult for multi-room audio systems if the adjustments are not located in the same room as the speakers. Also, the consumer may not recognize that clipping is occurring or want to be burdened with manually adjusting the volume for each song or source selected. Clipping can result in irreversible amplifier and/or speaker damage.
Audio processing systems can fail to operate due to improper installation or amplifier/speaker connections. For a residential multi-channel audio processing system, an amplifier connects to remotely located speakers via speaker wire running through residential walls. Common installer errors include mismatching speaker impedances with amplifier load ratings, complete or partial short-circuiting of amplifier outputs, amplifier overheating due to poor amplifier ventilation, and incorrectly set gain levels due to the remote location of the speakers. Diagnosing installation errors is complicated by the remote location of the speakers. Additionally, the remote and varied location of a speaker results in a variable speaker wire impedance further complicating amplifier/speaker matching. A typical audio processing system finds significant challenges in continuously monitoring and simultaneously correcting multiple sets of potential audio processing system failures, each one unique to the speaker configuration and wiring configuration.
The above and other difficulties in the implementation and operation of audio systems have presented challenges. In particular, damage to components of the audio system and/or improper audio signal delivery due to distortion or other conditions has continued to plague these and other related applications.